高温后混凝土软化本构曲线的确定

Determination of Softening Traction-Separation Laws after Exposure to High Temperature

结合高温后混凝土楔入劈拉法试验,采用3种常温下混凝土双线性软化本构曲线,借鉴常温下双K断裂模型中失稳韧度KIC,un,T与黏聚韧度KIC,c,T,起裂韧度KIC,ini,T间的定量关系,对高温后混凝土断裂韧度间的关系进行研究.结果表明:高温后黏聚韧度KIC,c,T的计算分为2种情况,用不同软化曲线计算得到的黏聚韧度值相近;由3种常温下的软化曲线计算得到的失稳断裂韧度值与实测失稳断裂韧度值能够较好吻合,现有软化曲线能较好地反映高温后混凝土断裂性能;同时验证了双K断裂模型对高温后混凝土的适用性.

Wedge-splitting tests of the concrete specimens after exposure to high temperature were conducted. Adopting three bilinear softening curves at room temperature and taking account of the quantitative relationship among unstable fracture toughness KIC,un T, initial fracture toughness KIc,ini,T and cohesive fracture toughness KIC,c,T from the double-K fracture model, the relationship of these three parameters for the concrete after exposure to high temperature was investigated. There are two cases of calculation of cohesive fracture toughness KIC,c,T, and the similar values of Kic,c,T are obtained from the calculation using different softening curves. The calculated unstable fracture toughness KIC,un T based on the three softening curves has a good coincidence with the experimental value, which shows that the softening curves could well reflect the real fracture feature of the concrete after exposure to high temperature and the adaptability of application of double-K fracture model to the concrete after exposure to high temperature is proved.